About 3 years ago, Mr Maple had a severe vertical split on his main trunk. In an attempt to save him, I began to wrap the wound with weed block fabric to help keep out insects and try to hold him together. Each Spring, I would change the wrap. This year, to my great surprise, pleasure and relief, I discovered he had sealed his wound. For an explanation of how trees treat wounds, here is an extract from a Northern Woodlands Magazine article by Michael Snyder:
In order to survive, trees must overcome their injuries. But technically they don’t heal their wounds, at least not the way that human and animal bodies repair, restore, or replace damaged cells or tissue. Trees are built in layers of cells that are bound by rigid walls in a modular, compartmented way. This structure dictates their wound response.
During each annual growth period, trees build their trunks and branches outward from a layer of actively dividing cells. Increments of new wood are added in a cone shape, enveloping the previous year’s smaller, cone-shaped increment. Picture stacked traffic pylons. Thus, trees grow ever upward and outward, in front of themselves, both in length and in girth.
When a cell is damaged, a tree cannot go back and fix or replace it. But it can limit the damage from any given injury by containing it and excommunicating it from the rest of the still-growing tree. The trick is in sealing, not healing. The focus is on resisting the spread of damage – especially infections of bacteria and fungi and the decay they cause – by isolating the wound and then growing beyond it.
Trees close wounds in two separate processes that create both chemical and physical boundaries around the damaged cells. First, they produce what is sometimes called a reaction zone, altering the chemistry of the existing wood surrounding a wound and making it inhospitable to decay organisms. Then, they build a barrier zone to compartmentalize the injured tissue with new tissue called “callus” or “wound wood” growing outward. If all goes according to plan, the callus growth covers and seals the wound and allows new uncontaminated wood to grow over and beyond it.
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